This is a fairly old story that periodically gets new life. The most recent buzz is based on a major study published this year in the American Journal of Clinical Nutrition that concluded cola, but not most other non-caffeinated carbonated drinks, is linked to bone loss. The study was conducted by researchers from several universities and supported by the U.S. Department of Agriculture.
What Did the Study Really Report?
First of all, this was not the type of study that conclusively shows that soda causes bone loss, and the study authors are very careful to point this out in their journal article. The study investigated associations between a variety of foods and bone mineral density (BMD). A food questionnaire was sent to study participants that asked how often they consumed various amounts of 126 food items. The information from these questionnaires was compared to each participant’s BMD measured by DEXA.Analysis of the results indicated that women who consumed the most cola-type sodas had significantly lower BMD at the hip, but not the spine. They found no similar association in men and there was no association between BMD of the women and consumption of other types of non-caffeinated sodas.
Why Would Cola-Type Sodas Affect Bones?
It's not known precisely why soda-like drinks were linked to higher bone loss in women in this study, and the authors note that more research is needed. But other studies have proposed that people who drink plenty of sodas are likely to drink fewer calcium-containing beverages like milk. However, this study did not find this to be the case.Two components found in cola -- but not in most other soda flavors -- are phosphoric acid and caffeine. Again, it's unclear if these two chemicals are the culprits.
The phosphorus part of phosphoric acid is a major component of bone mineral content, along with calcium. However, if phosphorus content of the diet is too high compared to calcium, it can alter hormone levels in a way that could increase bone loss. This should not be a problem if calcium intake is adequate.
Furthermore, caffeine can cause a very small reduction in calcium absorption. Some studies reported that caffeine also increases calcium loss in the urine, however this was later shown to be untrue when evaluated over longer periods of time. Bone health researcher Dr. Robert Heaney, professor of medicine at Creighton University in Omaha, Neb., put the caffeine issue into perspective, saying, “...the solution is not to decrease the caffeine intake of the Western world, but to provide adequate sources and intakes of calcium.”
Is Carbonation of Beverages Bad for Bones?
Carbonation (the addition of carbon dioxide gas to beverages) does not appear to have any effect on bone health. This is not surprising, since the body produces large amounts of carbon dioxide and is very efficient at releasing it in expired air. The amount of carbon dioxide in a carbonated beverage is rather minor compared to the amounts that the body produces.
Is Fructose in Soft Drinks Bad for Bones?
Some studies have indicated that high intake of fructose (from high fructose corn syrup) and other sugars can temporarily increase calcium loss in the urine. However, fructose does not affect total calcium loss when evaluated over a 24-hour period. So, as long as overall calcium intake is adequate, fructose is unlikely to be a significant factor.See next page for the bottom line on sodas . . .